Crystal structure of the layered arsenide Rb₃Cu₃As₂

The crystal structure of a new arsenide, Rb₃Cu₃As₂ (trirubidium tricopper diarsenide), has been established from single-crystal X-ray diffraction data. This compound crystallizes in the K₃Cu₃P₂ type, with layers of interlinked CuAs₂ units. The partitioning of the available valence electrons yields the charge-balanced composition (Rb⁺)₃(Cu⁺)₃(As^3-)₂, placing this phase in a broad field of transition-metal-containing Zintl phases. First-principles calculations confirm a semiconducting ground state, in accordance with electron-counting considerations. Chemical bonding analysis reveals strong covalent Cu-As bonds and ionic Rb...As interactions. In addition, a weak attraction is found between the Cu atoms, possibly pointing toward cuprophilic interactions.